Adding eEM1 and eEM2 into L1 menu for Heavy Ion runs

Merged Qipeng Hu requested to merge qhu/athena:NewThreshold-eEM-23.0 into 23.0

Two new phase-I low-threshold eEM items, i.e. eEM1 and eEM2, are introduced in athena:23.0 discussion following in ATR-26979.

Tagging menu coordinator @lidiaz and @astruebi for checking the implementation

Also tagging HI trigger menu coordinators @jkremer and @asmaga

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